The present disclosure relates to polishing slurry, and more particularly, to polishing slurry that is capable of being used for planarizing cobalt through chemical mechanical polishing in a semiconductor manufacturing process and a substrate polishing method using the same.
As semiconductor devices are gradually reduced in size, and the number of metal lines gradually increases, surface irregularity on each of layers may be transferred onto the next layer. Thus, surface roughness of the lowermost layer becomes more and more important. The roughness may have a serious influence on processes to cause such a difficulty as to perform a photolithography process in following processes. Thus, to improve yield of semiconductor devices, a planarization process for removing the roughness on the irregular surface, which occurs in several processes, may be essentially performed. The planarization process may include various processes such as a reflow process after a thin film is formed, an etch-back process after a thin film is formed, and a chemical mechanical polishing (CMP) process.
The chemical mechanical polishing process may represent a process of providing an abrasive and slurry containing various compounds to perform a polishing process on a surface of a semiconductor wafer while the surface of the semiconductor wafer contacts a polishing pad to rotate, thereby planarizing the surface of the semiconductor wafer. That is, the chemical mechanical polishing process may represent a process of chemically and mechanically polishing a substrate or a surface of a layer on the substrate by using slurry and a polishing pad to planarize the substrate or the surface of the layer on the substrate.
In general, in a process of polishing a metal, a process of forming metal oxide MOx by using an oxidizing agent and a process of removing the formed metal oxide by using an abrasive are repeatedly performed. A process of polishing a cobalt layer, which is increasing in utilization as a line for a semiconductor device, may also be performed by a mechanism in which a process of forming cobalt oxide by using an oxidizing agent and a process of removing the formed cobalt oxide by using an abrasive are repeatedly performed.
Also, an insulating film or a pattern such as a trench may be formed on a lower portion of the cobalt layer. In this case, high polishing selectivity between the cobalt layer and the insulating film is required in the polishing process. That is, slurry that well polishes the cobalt layer, but does not well polish the insulating film may be required.
In accordance with the related art, to polish the cobalt, alumina or silica particles are used as the abrasive, and slurry is used as the oxidizing agent. However, if the slurry is used, corrosion defects (corrosion pit) in which a surface of the cobalt is dug due to local corrosion on the surface of the cobalt may occur. The corrosion defects may have a bad influence on quality of the device to be manufactured. Thus, a method in which a corrosion inhibitor is additionally added to the slurry used for polishing the cobalt has been proposed. However, according to this method, compositions of the slurry may be complicated, and components of the slurry have a difficulty in control. Also, since the oxidizing agent is used as ever, it may be difficult to completely solve the corrosion limitation. Also, the slurry for polishing the cobalt in accordance with the related art may not sufficiently realize the polishing selectivity of the cobalt to the insulating film.
Slurry for polishing cobalt, to which a corrosion inhibitor is added, is disclosed in US Patent Publication No. 2013-00186850.